Over the last few years, reduction of gene expression (also referred to as “knockdown” or “gene silencing”) in multicellular organisms by means of RNA interference or “RNAi” has become a well-established technique. RNAi is a process of sequence-specific knockdown of gene expression initiated by double-stranded RNA (dsRNA) that is complementary in sequence to a region of the target gene to be knocked down (Fire, A. Trends Genet. Vol. 15, 358-363, 1999; Sharp, P. A. Genes Dev. Vol. 15, 485-490, 2001). Reference may also be made to International applications WO 99/32619 (Carnegie Institution) and WO 00/01846 (Devgen NV), and U.S. Pat. No. 6,506,559.
Gene silencing by dsRNA finds application in many different areas, such as dsRNA-mediated gene silencing in clinical applications (WO 2004/001013). The technique of RNAi has also been used to knock down gene expression in pests, including insects. Other published applications that relate to the use of RNAi to protect plants against insects include the International applications WO 2006/046148A2 (Devgen NV); WO 2006/045591A2 (Devgen NV); WO 2006/045590A2 (Devgen NV); WO 2006129204 (Devgen NV); WO 2001/37654 (DNA Plant Technologies), WO 2005/019408 (Bar Ilan University), WO 2005/049841 (CSIRO, Bayer Cropscience), WO 2005/047300 (University of Utah Research foundation), WO 2005/110068 (Monsanto), WO2007/035650 (Monsanto), WO2007/083193 (Devgen NV), WO2007/074405 (Devgen NV), WO2007/080127 (Devgen NV), WO2007/080126 (Devgen NV) and the US published application 2003/00150017 (Mesa et al).